In a time of blogs with their ethic of transparency, how long can journalists continue to hide their opinions? I'm a believer in the British newspaper model, in which print journalists join a tribe, Guardian left or Telegraph right, and then invite the public to judge them not on their hidden agendas, but on the quality of their journalism. British broadcast and all US news organisations, by contrast, expect us to believe journalists are devoid of opinions: half-human hacks, roboreporters.

That fiction is falling apart in the US presidential campaign, where news media have failed to cover one of the essential stories of the event: media's own love affair with Barack Obama.

The story has begun to attract attention, with comedy show Saturday Night Live twice skewering the press's roughing up of Hillary Clinton and fawning over Obama. In one skit, the show's faux Clinton complains: "Maybe it's just me, but once again it seems as if a) I'm getting the tougher questions and b) with me, the overall tone is more hostile."

The real Clinton picked up the punchline at the next debate and said: "If anybody saw Saturday Night Live, maybe we should ask Barack if he's comfortable and needs another pillow." Some believe this played a role in her victories last week.

In the other skit, a reporter gushes to "Obama": "I just really, really, really, really want you to be the next president." And the Fauxbama responds that journalists are "tired of being told, 'You journalists have to stay neutral, you can't take sides in a political campaign'. And they're saying, 'Yes, we can. Yes, we can take sides. Yes, we can.'"

So why don't they? The question of journalistic objectivity is the stuff of endless journalism-school seminars. But what's different this year is that the journalists' opinions are related to the quality of coverage of the campaign.

I've seen reporters complain Clinton doesn't give them access or is aloof; I've seen journalists quoted (anonymously) saying that they don't much like her. Of course, that shouldn't affect their coverage - since when do we see crime reporters whine that murderers are mean to them? - but it does. Obama is on an endless press honeymoon. He breathes rhetorical cumulus clouds - "Change we can believe in", "Yes, we can", "We are one" - without reporters challenging him or his supporters to define what they mean. I'll wager that if a pollster asked 1,000 Obama fans what "change" means, there'd be 100 different answers.

There's another new factor in the objectivity debate: weblogs. Reporters are now writing them. And they're learning that if a weblog is successful, it is a conversation held at a human level. That conversation demands frank interaction and openness. As one online executive puts it: blogs are a cocktail party. I'll add that if you talk to friends at a party and refuse to give your opinion while demanding theirs, someone will soon throw a drink at you, as I have been wanting to do to many a TV pundit lately.

I've heard TV news executives say that to have on-air personalities writing blogs might present a conflict because, after all, TV people are impartial. But they already live with that conflict by presenting TV journalists as personalities and then cutting off that part of the personality that enables opinion. If these people want to join the discussion on the net and reap its benefits, they have to give something of themselves.

The more journalists tell us about their sources, influences and perspectives, the better we can judge what they say. So I should tell you I voted for Clinton. You probably could have guessed that. But now you don't have to.

· Jeff Jarvis is a journalism professor at the City University of New York who blogs at buzzmachine.com